This invention was made in an effort to overcome certain disadvantages in the wiring harness of a sonobuoy, i.e. an array of hydrophones in an underwater sonic detection system. While the invention is especially useful in such systems, it may also find use in other applications. In sonobuoys it is common practice to deploy an array of hydrophones in a suspended arrangement from a single flotation device. A wiring harness with multiple tap points is suspended from the flotation device and the number of wires in the harness diminishes from the upper end to the lower end with a hydrophone connected to the lower end of each of the wires. This type of sonobuoy is sometimes referred to as a vertical line array and the wiring harness is known as a tapered harness because of the diminishing number of wires.
The wiring harness for a tapered array must have the attributes of high strength, small size and light weight. The strength is required to support the ballast which tends to keep the harness vertical in the water and light weight is desired to minimize the load on the suspension system. A compact, circular cross-section of the harness is desirable to minimize the lateral drag forces due to currents in the water which induce motion of the harness.
It is known that acoustic noise is generated by flow currents around the wiring harness. The magnitude of the noise increases with the diameter of the harness and with other factors. The shedding of vortices indirectly produces the acoustic noise. It is known that hairing on the harness will reduce the noise by inhibiting the formation of vortices in the flow around the harness. Hairing is made up of a multiplicity of hairing members, each comprising a length of multifilament thread, spaced along the harness. An increased amount of hairing, i.e. closer spacing of hairing members, for increased diameter of the harness will reduce the noise but it also increases the drag on the cable due to current flow. This additional drag is undesirable since it will distort the shape and the attitude of the acoustic array. This distortion has a deleterious effect on the beam pattern formed by the hydrophones fastened along the length of the harness.
A general object of this invention is to overcome certain disadvantages of tapered wiring harnesses for underwater acoustic arrays of the prior art.